A: I made 5,127 prototypes of my vacuum before I got it right. There were 5,126 failures. But I learned from each one. That’s how I came up with a solution. So I don’t mind failure. I’ve always thought that schoolchildren should be marked by the number of failures they’ve had. The child who tries strange things and experiences lots of failures to get there is probably more creative.

Not all failures lead to solutions, though. How do you fail constructively?

A: We’re taught to do things the right way. But if you want to discover something that other people haven’t, you need to do things the wrong way. Initiate a failure by doing something that’s very silly, unthinkable, naughty, dangerous. Watching why that fails can take you on a completely different path. It’s exciting, actually. To me, solving problems is a bit like a drug. You’re on it, and you can’t get off. I spent seven years on our washing machine [which has two drums, instead of one].

What’s the main lesson from those 15 years’ developing the vacuum?

A: It can take a very long time to develop interesting products and get them right. But our society has an instant- gratification thing. We admire instant brilliance, effortless brilliance. I think quite the reverse. You should admire the person who perseveres and slogs through and gets there in the end.